Matting of melt-spun amorphous polymer filaments and process

ABSTRACT

PRODUCTION OF A MATTING OF MELT-SPUN SUBSTANTIALLY AMORPHOUS AND CONTINUOUS FILAMENTS BY DEPOSITING THE FRESHLY SPUN FILAMENTS ONTO THE SURFACE OF A COOLING BATH TO FORM OVERLAPPING SELF-ADHERING LOOPS IN AT LEAST THREE ROWS OR LAYERS, THE LOOPS BEING ORIENTED AT DIFFERENT ANGLES BY ADJUSTING THE WITHDRAWAL OF THE FILAMENTS IN A DIVERGING PATH THROUGH THE BATH, E.G. WITH THE USE OF A SUPPORTING GUIDE PLATE IN CONTACT WITH AN OUTERMOST ROW OF FILAMENTS. THE PRODUCT IS A LIGHTWEIGHT, COHERENT MATTING OF SELFBONDED, LOOPED FILAMENTS AND IS ESPECIALLY USEFUL IN CONSTRUCTING ARTIFICIAL SKI SLOPES AND AS A REINFORCEMENT FOR TRANSPORTABLE TURF.

Sept. 12, WERNER ET AL MATTING OF MELT-SPUN AMORPHOUS POLYMER FILAMENTS AND PROCESS Filed Nov. 21, 1969 2 Sheets-Sheet 1 FIG.

FIG. 2

INVENTORS m w P T w ham CLAW Sept. 12, 1972 WERNER ET AL 3,691,004

MATTING 0F MELT-SPUN AMORPHOUS POLYMER FILAMENT AND PROCESS Filed Nov. 21, 1969 2 Sheets-Sheet 2 4 WW w z w ATT'YS Patented Sept. 12, 1972 United States Patent Ofiice 3,691,004 MATTING F MELT-SPUN AMORPHOUS POLYMER FILAMENTS AND PROCESS Helmut Werner, Elsenfeld, and Hans-Stapp, Momlingen, Germany, assignors to Akzona Incorporated, Asheville,

Filed Nov. 21, 1969, Set. No. 878,615 Int. Cl. D04b 3/16, 1/04 U.S. cum-150 27 Claims ABSTRACT OF THE DISCLOSURE Production of a matting of melt-spun, substantially amorphous and continuous filaments by depositing the freshly spun filaments onto the surface of a cooling bath to form overlapping self-adhering loops in at least three rows or layers, .the loops being oriented at different angles by adjusting the withdrawal of the filaments in a diverging path through the bath, e.g. with the use of a supporting guide plate incontact with an outermost row of filaments. The product is a lightweight, coherent matting of selfbonded, looped filaments and is'especially useful in constructing artificial ski slopes and as a reinforcement for transportable turf.

It is well known that filamentary or fibrous matting can be prepared from a wide variety of natural or synthetic fibers, including both organic and inorganic fibers. In general, the individual filaments used for this purpose are non-amorphous or relatively high oriented fibers which are randomly incorporated into the matting to form a felted or non-woven structure with or without a bonding of the filaments to each other. The resulting structures are usually made up of a relatively dense collection of cut fibers to provide a more or less resilient, flexible and soft matting having textile-like properties. A stiflening of the matting can be accomplished by using adhesives, bonding agents or laminating materials, e.g. by partly or completely impregnating the fibrous structure with a hardenable 0r fusible substance. Such known structures the points of contact or intersection. -Yet another object of the invention is to provide a method or means of varying the resiliency and density of the matting in a controlled manner as well ascontrolling the size and angular position of filamentary loops in the matting. The invention has as further objects the production of special types of matting adapted to particular areas of utility by reason of their novel and unique structure. These and other objects and advantages of the invention are explained in greater detail in the following detailed disclosure.

In accordance with the invention, it has now been found that a highly durable matting of substantially amorphous and continuous thermoplastic polymer filaments can be produced in a controlled manner by following the steps which comprise: melt-spinning said filaments with a diameter of about 0.1 to 1.5 mm. vertically downwardly for deposit onto the bath surface of a liquid cooling medium from a plurality of spinning orifices arranged in at least three adjacent rows of approximately. equidistantlyv medium being sufiicient to cause said filaments to spread laterally in the form of sinuous loops overlapping each other with reference to adjacent filaments in at least the same row; completely solidifying the freshly spun filaments only after their entry into said cooling medium such that near the surface of the cooling medium the filaments remain sufiiciently tacky to adhere to each other at their overlapping points of intersection; continuously withdrawing the melt-spun filaments through said liquid cooling medium in a path which diverges from the vertical direction of said melt-spinning such that an outermost row of filaments forms a bottom layer of overlapping selfadhering looped filaments, each of the remaining rows of overlapping self-adhering looped filaments being positioned on top of and in adherent contact with the next underlying row, the point at which the direction of withdrawal of filaments diverges from the vertical direction of melt-spinning being located in a zone extending from about the surface of said bath down to a distance below said surface where said filaments are still sufficiently plastic to be deformed; and removing the resulting mass of looped and layered filaments from said bath of liquid cooling medium after the filaments have solidified sufficiently for adherent bonding into a continuous coherent matting.

The term substantially amorphous is applied to the filaments employed herein to designate those filaments which have a crystalline proportion which amounts to not more than 30% and preferably less than 20%. This amorphous characteristic of the filaments is a well known property which can be easily determined by conventional methods. In the normal melt-spinning and stretching of thermoplastic filaments, a high degree of molecular orientation is achieved so that the initially amorphous polymer acquires a correspondingly high crystallinity. During the process of the present invention, the freshly spun molten filaments are deposited loosely and without any tension onto the surface of the cooling bath so that they inherently retain their amorphous character, Also, it is preferable to avoid any substantial tension capable of stretching the filaments as they are Withdrawn through the cooling bath so that the amorphous character of the initial polymer is largely retained.

The term buoyant force as used in connection with the liquid cooling medium is intended to include not only the upward force exerted upon an immersed body in a liquid but also surface tension forces which may act to support the body on the surface of the liquid. The generally sinuous to helical looping of the freshly spun and relaxed filaments as they enter the liquid cooling medium can be attributed to one or both of these forces, although the exact mechanism is not fully understood. It is apparent, however, that looping begins at the surface of the cooling liquid, and as the filaments sink below'this surface and are withdrawn in a path diverging from the vertical melt-spinning direction, a large number of separated and relatively uniform loops and tend to form continuously in a predominantly sinuous configuration. The angle of these loops with reference to the top and bottom sides of the finished matting can be controlled by the angle of divergence of withdrawal and also by other preferred measures.

For reasons of economy and simplicity of the process, water is most advantageously used as the cooling liquid, but substantially inert liquids other than an aqueous medium can also be employed.

The filaments being looped and formed into the matting of the invention can be produced from any melt-spinnable synthetic linear fiber-forming polymer, including polyamides, polyesters, polyolefins and the like, preferably non-elastomeric polymers. For particular purposes in terms of the utility of the finished product, it is especially advantageous to employ conventional polyamides, e.g. polycaprolactam and polyhexamethylene adipamide (nylon 6 and nylon 6,6). Pigments, dyes, anti-static agents, light and heat stabilizers and other well-known additives can be incorporated in the polymer in the usual small amounts. Other modifications of fiber-forming polymers and copolymers may also be adopted within the scope of the invention.

The molten polymer can be spun or extruded with conventional apparatus onto the surface of the cooling liquid from a multi-aperture spinneret having at least three rows of spinning orifices with an equidistant spacing of the orifices in the same row to permit a lateral overlapping of the formed loops in a generally uniform manner. This spacing should normally fall in a range of about 2 to 20 mm., preferably about 3 to 15 mm., depending upon the diameter of the filaments and the size of the loops being formed as well as the desired density of the finished product. It is preferable to maintain this same equidistant spacing between the orifices in adjacent rows while using the same diameter of filaments from all orifices, so that the filament loops overlap from row to row as well as in the same row. However, minor modifications of this arrangement can occur as explained more fully hereinafter.

One of the outermost rows of filaments can be selected as the base or bottom side of the matting, and as this row is deposited on the surface of the bath with the formation of laterally spreading loops which intersect and bond to one another, a coherent base layer of looped and bonded filaments is immediately formed at or near the surface of the bath. Depending on the temperature of the molten polymer and the temperature of the bath, the looped filaments can remain tacky and self-adhering over a short distance below the surface of the bath. This can be identified as the bonding zone of the bath wherein subsequently deposited rows of looped filaments are still sufficiently tacky to adhere at the points of contact or intersection with the next underlying row of filaments. As the filaments continue through the bath, they become more solid so as to lose their tackiness but retaining sufficient plasticity to be deformed. This can be identified as the plastic zone of the bath wherein the formed loops can still be shaped or rearranged in their relative portions of orientation, i.e. at various angles. The divergence of the withdrawal path must occur at least within this plastic zone and preferably within the bonding zone.

Each row or layer of filaments follows a path of withdrawal along a plane which forms an acute diverging angle from the vertical plane of melt-spinning, i.e. as though the plane of melt-spinning were to be inclined around a horizontal axis along the row of filaments. The amount of inclination or angle of divergence can feasibly amount to as much as 90 but is preferably maintained within about 10 to 80. After the base layer or bottom layer of filaments is formed in this manner, each successive row is deposited on top of the inclined slope of the next layer below in contacting or preferably overlapping and intersecting relationship of adjacent loops.

With only a slightly spread path of divergence, it is desirable to space the rows of filaments closely enough to permit an overlapping of loops from row to row. On the other hand, with a wide angle of divergence corresponding to a more horizontal withdrawal of the filaments, the rows of filaments can be spaced at relatively greater distances apart without initial overlapping on the surface of the bath, particularly where the point of divergence is maintained within the bonding zone of the bath for all rows of filaments. In this respect, it is also possible to vary the diameter of the filaments from row to row or even within the same row to produce variations in the loops and the structural density of the matting, provided that there is sulficient bonding between all adjacent filaments to yield a coherent matting.

The matting produced according to the invention can have a relatively uniform structure in which the density is uniform along its length, width and height, the loops being disposed in substantially the same direction over an entire cross-section, i.e. predominately toward the top and bottom surfaces of the matting. With this uniform structure, the matting of the present invention is closely related to the cushioning structure disclosed in our copending application, Ser. No. 807,301, filed Mar. 14, 1969. The procedure followed is then also quite similar to this copending application which is therefore incorporated herein by reference as fully as if set forth in its entirety. The cushioning structure of this copending application is intended to provide helical to sinuous loops arranged around a vertical axis, similar to the coiled springs of a mattress core, so as to provide a high degree of resiliency in this 'vertical direction. By comparison, the present invention provides loops arranged more nearly around a horizontal axis or with varying positions from top to bottom of the finished matting. This results in a more rigid structure in the vertical direction of use, but with varying amounts of resiliency and flexibility in a controlled fash- For example, the structure of the matting according to the invention can be such that the loops lie horizontally or substantially horizontally and form a more solid or rigid association on the bottom side of the matting, while the layers of loops decrease in density towards the top surface and the upper loops form an angle of up to 90 relative to the horizontal.

In another form of resilient matting according to the invention, the loops lie horizontally or substantially horizontally and form a relatively solid or rigid structure on both the bottom and the top sides of the matting, while the loops inside the matting form an angle of up to 90 relative to the horizontal.

In one modification of the process for reorientation of the loops, the group of filaments being deposited and looped on the surface of the bath is brought almost simultaneously into contact with a guide or supporting body which has a smooth surface and which intersects the surface of the bath at an angle of from about 10 to in such a way that the filaments of one of the outermost rows of the group of filaments impinge substantially on the sectional line along which the surface of the bath is intersected by the body. It is preferred to use an arrangement in which the filaments of one of the outermost rows of the groups of filaments impinge more or less exactly on this sectional line. In this way, the loops of filaments which form on the bottom surface of the matting coming into contact with the inclined body are particularly uniform and lie horizontally or substantially horizontally in a dense or more rigid association of fiat loops. If the point or line at which the outermost row of filaments come into contact with the body is displaced somewhat below the surface of the water, the resulting matting again has a relatively smooth and flat surface except that the loops though substantially horizontal are spaced further apart such that the matting is less dense.

The filaments of the outermost row can alternatively be brought into contact with the guide or supporting body slightly above the line where the surface of the bath is intersected by the body. In this case, however, more cooling liquid must be delivered over the supporting body to the group of exposed filaments. The linear interval between the points at which the filaments of the outermost row come into contact with the body and the sectional line between the surface of the bath and the supporting body should at most be equal to the linear interval between the outermost row and the next adjacent row of filaments.

It is preferred to use a smooth flat plate to carry out these modifications of the process for the production of matting with a smooth bottom surface. However, it is alternatively possible to use curved plates or rollers, although in this case the radius of curvature of the plate or the diameter of the roller should be sufiiciently large for the filaments to be inclined from the horizontal for a certain distance at a substantially constant angle, after they come into contact with the body.

If it is desired to produce a continuous length of matting which shows a horizontal or substantially horizontal loop orientation on both the bottom and the top sides, this can be achieved by bringing one outermost row of filaments into contact with the supporting plate, while alight pressure is allowed to act on the matting being formed from the opposite or top side by means of a rotatable roller. Appropriate measures should be taken to ensure that the filaments coming into contact with the roller, though still plastically deformable, are no longer sticky or tacky in any way. This is preferably accomplished by mounting the roller in such a way that it is at least partly immersed in the bath liquid. I

There are several other Ways of highly affecting the properties of the matting. For example, rollers can be positioned on either or both sides fthe matting in the plastic zone of deformation to provide a light pressure on the surface loops, and all such contacting plates or rollers may be internally heated, e.g. where the bath temperature is too low or where the filaments require additional heat to maintain their plasticity. However, in all g I such modifications, care must be taken to ensure that the filaments during formation of loops are still in astate in which they can be at least superficially bonded together at the places where they cross one another.

First and foremost the diameter of the filaments should be mentioned as a primary factor in achieving a selfadherence or melt-bonding of overlapping or contacting filaments. The use of very fine filaments is not satisfactory but the diameter can vary widely between about 0.1 and 1.5 mm. Naturally, the thickness of the filaments is primarily determined by the rate at which the melt is delivered, by the number of bores or ducts in the spinneret and the diameter of its openings. In addition, the diameter of the filaments can be regulated, although to a lesser extent, by the interval between the base of the spinneret and the surface of the bath. Generally, it can be said that relatively thin filaments within the above-noted range produce relatively softer mattings.

Both the density and the resilience of the matting are also influenced by the diameter of the filaments. Quite apart from other factors, it has been found that the thinner filaments generally form a relatively denser structure, While the loops being formed will increase in size with increasing filament diameter, thereby providing a more open matting of fairly bulky structure under otherwise the same process conditions.

The distance between the base of the spinning orifices and the surface of the bath can be between about 2. and 30 cm., although it is preferably maintained between about 4 and cm. The smaller this distance or free space, the flatter and more densely will the loops of filament be deposited. It will be readily appreciated that with filaments of relatively coarse denier (large diameter), it is generally not advisable for this distance to be at the lower end of the specified range. On the other hand, the distance between the base of the spinning orifices and the surface of the bath should be no more than about 15 cm. when using relatively fine filaments. In either case, it is important not to operate outside of the specified limits. If the spinneret base were to be placed at a distance, of less than 2 cm. from the bath surface, evaporation of the cooling liquid would be excessive on account of the high temperatures of the spinneret. Distances in excess of cm. are not practical because the filaments would be excessively cooled before they reached the surface of the bath, with the result that the filaments would not be deposited in the form of loops, as required, but also they would not be adequately bonded at their points of contact or intersection. 1

:Both the nature and the properties of the matting can also be influenced by the numbers of rows of filaments and by the intervals between the openings of the spinneret. It is surprising that matting can be made sufliciently coherent simply by extruding three rows of filaments. An obvious requirement in this case is that the intervals between the spinneret openings should not be too excessive and that the individual filaments should not be of too small a diameter. Matting of limited depth and extremely open structure may be used for example as an impactor shock-absorbing material in the shipping of sensitive or fragile goods. After it has been produced, the matting can be coated or impregnated with a rubberizing composition, and it can then be used as a non-slip underlay for carpets or other fioor coverings. Still other novel products and uses are defined hereinafter.

The modification of the process described above in which a plate or the like is inserted into the cooling bath, is particularly applicable where it is desired to make a relatively thick matting from a large number of rows of filaments. It is possible to make different kinds of matting simply by varying the inclination of the plate with respect to the surface of the bath.

In one particular embodiment of the process, the filaments 'of one of the outermost rows of the group of filaments are brought into contact with the plate substantially along the sectional line between the surface of the bath and the plate. The filaments of this outermost row which are still highly plastic when they come into contact with the plate and the surface of the bath are laid substantially fiat by contact with the plate. In other words, the loops formed lie parallel or substantially parallel to this bottom surface of the matting facing the plate. In addition, these flattened loops are joined more firmly together than the remaining loops because the points where they overlap and intersect one another are situated closer to one another. The smaller the angle which the plate forms with the surface of the bath, the more conspicuously the position of the remaining loops will be influenced. Whereas matting made in the absence of a plate or the like will have a generally uniform structure and approximately the same density throughout its entire cross-section, matting produced using a plate varies in density. The density increases towards the bottom surface, i.e. towards that surface which comes into contact with the plate during the manufacturing process.

In addition, the layers of looped filaments are differently oriented when using this plate. The angle which the loops form'with the smooth bottom side of the mat increases towards the top. Whereas the lowermost loops are always horizontal or substantially horizontal with reference to the base or bottom of the mat, irrespective of the inclination of the plate, the loops being formed towards the top or upper portion of the mat have an angle from the horizontal which is greater with a steeper inclination of the plate. Where the angle between the surface of the bath and the plate is about 75, the angle between the loops and the horizontal can be as much as provided that the position of the loops is not affected in any other way. Such an additional effect can be achieved, for example, by bringing the filaments on the upper or opposite side into contact with a rotating roller by means of which'a deforming pressure can be exerted on the matting. In this Way the structure of the matting can be consolidated and the position of the loops can be influenced at the same time as indicated above. It is thus possible to produce a matting whose top and bottom surfaces appear relatively flat and smooth.

' The process is further illustrated in conjunction with the accompanying drawings in which:

the axes of the five spinning bores, and illustrates one embodiment of the process of the invention;

FIG. 2 is a partially schematic and cross-sectional view similar to FIG. 1 to illustrate those embodiments in which a guide plate is mounted in the bath;

FIG. 3 is an enlarged view of a small portion of the bath and guide plate shown in FIG. 2 taken in the immediate vicinity of the point at which the plate intersects the bath; and

FIGS. 4-7 represent'side elevational views of a number of different matting structures.

Referring first to FIG. 1, the molten polymer is spun in a conventional manner from a spinning head 1 through spinneret or nozzle plate 2 containing at least three rows of bores 3, e.g. five rows as actually shown, with their spinning openings or orifices facing downwardly from the lower horizontal face of the spinneret 2. The spinning head can be attached in a conventional manner to an extruder capable of conveying the polymer to the point of spinning, and this spinning head is easily mounted for adjustment of its position in a vertical direction.

Five rows of molten filaments a, b, c, d and e are thus spun vertically downwardly onto the surface 4 of a water bath 5 contained in a suitably large vessel 6. The filaments are permitted to fall freely through the air gap between the base 2' of the spinneret and the surface 4 of the water. The liquid level in the vessel can be maintained constant by any conventional means, and the temperature of the bath is also kept approximately constant by means of a heat exchanger or the like (not shown). Rapid or turbulent circulation of the bath liquid should be avoided, particularly in the vicinity of the points where the filaments enter the bath. The optimum bath temperature depends upon the particular polymer and the extent to which the freshly spun filaments must first retain their tackiness or ability to bond to each other and then retain sufficient plasticity to be deformed. For example, with polyamide filaments, the temperature of the bath may vary between about C. and 50 C.

The openings in each of the five rows of spinning orifices corresponding to bores 3 are equidistantly spaced so that loops being formed at the surface 4 of the bath overlap one another and adhere at their points of intersection. The outermost row a of filaments falls relatively freely below the surface of the bath and is then diverted in its path of withdrawal by an angle of almost 90 to serve as a base layer on which the remaining rows of filaments are sequentially deposited from the bath surface. Where the interval between adjacent parallel rows of freshly spun filaments is greater than the lateral spreading of the loops at the surface of the bath. The point of divergence of the withdrawal path of row a is preferably maintained only a short distance below the surface of the bath where the filaments in all rows remain tacky so that a bonding occurs between adjacent rows of filaments. Otherwise, the rows are preferably spun at intervals which are closer together and permit an overlapping of loops between adjacent rows at or in the immediate vicinity of the surface of the bath.

The looped and layered rows of filaments are then conducted in self-adhered form 8 in the direction of the arrows beneath the surface of the bath until they have completely solidified and are then withdrawn from the bath around a pin or roller 9 by suitable conveyance means such as the nip rollers 10 and 11. When the resulting matting is sufficiently flexible, it can be wound onto a take-up roll, or else it can be cut to suitable lengths.

The speed of the rollers 10 and 11 should be adjusted to just take up any slack in the horizontally conveyed product, i.e. so as to avoid any tension which might pull the freshly spun filaments as they are being deposited and formed into looped and interbonded rows and layers. A slight sag or downwardly bowed path of withdrawal is preferred as compared to placing too great a tension on the filaments. The most desirable withdrawal rate together with the optimum spinning rate can be readily determined by routine tests.

An especially preferred embodiment of the process of the invention is illustrated in FIG. 2 where the withdrawal pin 9 and conveyance means 10, 11 have been omitted since they are clearly shown in FIG. 1. In this instance, the individual parallel rows of filaments a, b, c, d and e are spun vertically downwardly as discussed above' with loops being formed at the bath surface 4 in overlapping relationship as between filaments in the same row and in adjacent rows. An inclined smooth surfaced metal plate 12, preferably with a highly polished upper surface, extends downwardly in the 'bath at an angle of about 45 so as to intersect the surface of the bath along the line projected on this bath surface by the vertical plane of the outermost row a of the filaments. If desired, this plate can be internally heated, cg. with an electrical resistance heating element 13 connected externally of'the bath by suitable wires 14.

As the outermost row a of filaments impinge on the plate 12, loops are simultaneously formed and also distorted or deformed from a normally horizontal orientation with reference to the bath surface 4 to conform to the flat surface of the plate. Succeeding rows of deposited and looped filaments are deformed by a gradually lesser extent as they are farther removed from the plate. Withina' relatively short distance, the looped and self-adhered layers of filaments can be withdrawn from the plate and conveyed through the bath until the filaments are completely solidified. Immediately after leaving the plate 12,

the bottom row or base layer of filaments 15 exhibits loops It is also possible to exert a light pressure on the upper-' most row or layer of looped filaments by means of a rotating cylindrical roller 17 (shown in dotted lines) mounted on a vertically adjustable shaft 18 so that this roller can be placed at the desired depth in the bath. The upper loops will then also be flattened to lie more parallel with the upper side of the matting as indicated at 19, provided that these filaments are still plastically deformable as they pass under the roller 17. By rotating this roller 17 in the counterclockwise direction shown by the arrow, a further beneficial effect is obtained by ensuring a lack of tension on the filaments as they slide down the inclined plate 12. Also, it is desirable to provide means of adjusting this plate 12 as to its inclined slope and its position relative to the first row a of spun filaments.

Thus, in FIG. 3, the vertical plane a of the first row of freshly spun filaments is preferably positioned exactly along the line at which the plate 12 intersects the surface 4 of the bath 5. However, the plate 12 may also be moved to the right so that the vertical plane a of the first row of filaments is shifted correspondingly to the right and these filaments are then brought into contact with the plate just below the surface of the bath. Alternatively, the guide plate 12 can be moved to the right with the vertical plane a" of the first row of filaments crossing the plate just above the surface of the bath. In this latter case, the linear distance between the points of contact of the first row of filaments a and the surface of'the bath along the plate should not amount to more than the linear distance between this first or outermost row of filaments and the next adjacent row b (as viewed in FIG. 2). In other words, if a" represents the actual vertical plane of the first row of filaments, as shown in FIG. 3, then it is displaced above the bath by its maximum linear distance along the plate where plane a then represents the second row of filaments. Furthermore, where the filaments in plane a" come into contact with the plate above the surface of the cooling bath, it is desirable to pour additional cooling liquid over the inclined surface of the plate 12 by means of a slotted conduit 20 or similar means of liquid supply. This addition'liquid is preferably 9 heated to the prevailing bath temperature or maintained at this temperature, e.g. by recirculation from the bath itself. Even a relatively thin film of liquid on the upper surface of the plate 12 is sufiicient to prevent the freshly fices at the base of the spinneret; Examples 6 to 8 illus trate the effect oft he take-off rate; and Examples 9 and 10 demonstrate the effect of the gap between the surface of the bath and the base of the spinneret.

TABLE I Interval Gap between between spinneret Resilience Delivery Removal spinneret No. of and bath Filament Weight of Height of (loss of rate, rate, holes spinneret surface, diameter, matting, matting, height, g. lnnn. m./min. in mm. holes cm. mm. g./m. mm. percent) 600 3. 6 240 15 0. 3 1, 900 30 26. 6 600 3. 5 I5 36 1.0 1, 800 12 16. 5 600 3. 5 12 60 10 0. 9 1, 750 20. 0 600 3. 5 6 122 10 0. 4 1,800 25. 0 600 3. 5 5 168 10 0. 2 1, 800 22 27. 1 600 4. 8 5 168 10 0. 1, 450 15 20. 0 600 6. 2 5 168 10 0. 25 1, 170 12 16. 5 500 9. 0 5 168 10 O. 25 900 8 12. 5 600 3. 5 5 168 12 O. 25 1, 850 22 22. 7 600 3. 5 5 168 14 0. 25 1, 900 19 21. 0

NOTE.In the above table, the loss of height in percent which a 10 em. sample undergoes following the removal of a 10 kg. load previously placed on it, is quoted as a measure of resilience. In all the tests, the diameter of the spinning orifices or holes in the spinneret was 250 microns and the number of rows of holes was five.

spun filaments from adhering to the plate over the relatively short exposed distance.

EXAMPLES The following examples were carried out with the apparatus and procedure illustrated in FIG. 1, i.e. with the inclined plate omitted. In each of these first ten examples, summarized in Table I below, individual conditions have been varied while following the same general procedure set forth in the first example.

Example 1 Examples 11 to 16 A polycaprolactam melt is spun onto a waterbath into which a polished metal plate has been inserted as shown in FIG. 2. The filaments a of one of the outermost rows of the entire group of filaments make contact with the surface of the bath along the line where this surface is intersected by the plate 12. The angle between the surface 4 of the bath 5 and the plate 12 is 45". The loops formed at the surface of the bath are deflected by the plate from the vertical line or plane of free-fall. The loops of the first row a of filaments lie parallel with the plate and form a smooth bottom surface in the matting. The loops of rows b to e exhibit angles which increase gradually relative to the horizontal, i.e. with respect to top and bottom sides of the matting. The angle of the loops in the rows of filaments d and e at the top of the matting thus fall between 45 and 85, depending upon the process conditions. Particulars of the tests and the results obtained from them are set forth in Table II.

TABLE II Interval Gap between Resilience Angle o Delivery Removal between No. of spinneret and Filament Weight of Depth of (loss of loops in rate, rate, holes, rows of No. of bath surface, diameter, matting, mattlng, height, row 4 or 5, g./min. m./min. mm. holes holes cm. mm. g./m. mm percent) degree Norm-The tests in Table II demonstrate in particular that the properties of the end product such as its weight, height, resilience and the position of the layers of loops can be influenced to an appreciable extent merely by altering the dehvery rate of the melt and/or the removal rate. The resilience is measured as in Table I.

schematic longitudinal section of this arrangement is comparable to that shown in FIG. 1. The freshly spun filaments are deposited on the surface of the bath in the form of overlapping loops which adhere together at the points where they cross one another. The filaments have a diameter of 0.3 mm. and are substantially amorphous since they are spun without stretching. The loops thus formed sink slowly into the cooling liquid where they are consolidated into the layered structure of the matting and the resulting structure solidifies completely. After travelling through the bath for a distance of 100 cm., the matting is removed therefrom. The loops are distributed at random, although most of them preferentially lie almost perpendicularly to the direction of travel of the matting.

The matting product weighs 1900 g. per square meter for a thickness of around 30 mm. Density and structure are substantially uniform throughout the entire crosssection, all the surfaces have loops projecting from them.

Examples 2 to 10 The procedure of Example 1 is repeated with some of the conditions modified. Matting is obtained having the properties set forth in Table 1. Examples 2 to 5 demonstrate the effect of the interval between the spinning ori- As will be apparent from the foregoing examples, it is possible when using the process of the invention to produoe mattings having a wide range of properties and with variations in the position or orientation of the individual layers of looped filaments over a cross-secton of the matting. On the other hand, it will be recognized that all of the mattings have a number of characteristics in common, including a limited range in the diameter of individual filaments and the size of the loops. In general, the loops are proportionately large and provide a very open structure in the matting. Since adjacent filamentary loops must overlap one another, even the finest diameter filaments should contain loops which extend for at least 1 mm. and preferably 2 mm. or more, the larger diameter filaments normally extending to a much greater degree. As a rule, then, the loop extension should be at least about 10 times the individual filament diameter. The upper limit of this loop extension is preferably adjusted so that the overlapping between adjacent filaments is just sufiicient to ensure adequate bonding at random points of intersection.

The matting product represented in FIG. 4 is produced from only three rows of looped and self-bonded filaments according to the process illustrated in connection with FIG. 1. Such thin and highly flexible mattings with the loops projecting almost perpendicularly to the top and bottom surfaces can be readily produced in the form of wide sheets and used as separator sheets for packaging or as resilient underlaying for floor coverings, e.g. after being impregnated with an elastomeric polymer or even in combination with natural rubber. With large diameter filaments such a structure can be made with very little resiliency in the vertical direction while still retaining a high degree of flexibility in the horizontal direction.

The matting products shown in FIGS. 4-7 are produced from a number of rows of looped and self-bonded filaments according to one of the embodiments of the process illustrated in FIG. 2. The varying angle of the loops from bottom to top as shown in FIGS. 5 and 7 is caused by the insertion of the guide plate at an inclined angle in the bath, i.e. to provide a relatively smooth and flat bottom surface and a gradually increasing angle of the loops toward the upper surface. The top surface may also be fiattened as shown in FIG. 6 by the pressure of a suitable roller while these loops are still plastically deformable.

UTILITY While the matting products of the invention have a large number of useful applications, there are two distinct and novel areas of utility which are especially advantageous.

(1) Transportable turf.It has become quite conventional to establish new lawns or grassed areas by covering the soil with a pregrown turf rather than directly sowing grass seeds. In most cases, relatively small sections of a newly established turf are merely cut and transported to a new site together with a large amount of adherent soil. More recently, attempts have been made to embed lengths of non-woven fabrics or latticed or grid-shaped mats in humus soil and then pregrow the grass in this substrate. After an initial growing period with watering and cutting of the grass, a length of lawn is then rolled up and transported to the desired area of ground. The use of such supporting mats is accompanied by a number of disadvantages. For example, due to the completely flat nature of the fabrics or mats, they are unable to retain the humus soil and cannot be properly laid on uneven surfaces. The soil is often washed away or causes irregular distribution during seeding. The tensile strength of fabrics, even if they are relatively deep and expanded, is limited so that the lengths of grass are easily damaged when being rolled up, transported or relaid.

The matting structure of the present invention completely solves these problems and provides an excellent means of preparing and using a transportable turf. In general, it is sufiicient to use a matting corresponding to that represented in FIG. 4 as obtained by spinning the filaments in only about three to five rows, i.e. to provide three or more layers of overlapping and self-adhering looped filaments. The individual continuous and substantially amorphous filaments are melt-spun with a diameter of from about 0.1 to 0.8 mm., preferably about 0.2 to 0.5 mm. Polyamide filaments have especially favorable properties although other melt-spinnable thermoplastic polymers can also be used, e.g. polyesters or polyolefins. As a supporting or reinforcing structure for the turf, the mat according to the invention preferably weighs from about 150 to 500 grams per square meter and has a thickness of about 0.5 to 2.5 cm. The density and stiffness of the mat can be varied within relatively wide limits but retains sufficient flexibility for easy rolling of the pregrown turf.

To produce a length or strip of the desired sod or turf, the supporting mat of the invention is first placed on a reasonably smooth surface which together with the thickness of the mat should be such that the roots as they de-' velop do not get any substantial hold on the subsoil. It is particularly advantageous to provide the mat with a film or foil backing, e.g. made of a suitable inert polymer such as polyethylene, and this backing can have a sufficiently large number of openings for draining off excess water. The top soil is then applied to substantially fill the matting structure up to or slightly above its top surface, and grass seeds are then planted and tended in the usual manner.

No difficulties are involved in cutting the fresh seedlings of this filamentary reinforced turf, even with relatively heavy machines. The roots form a thickly entangled layer both inside and to some extent below the reinforcing mat. The length of pregrown turf can then be rolled up, preferably with the backing film or foil as a complete unit, and transported to the site of installation. The relatively expandable length of matting or turf strip tends to lie fiat even where the ground is irregular. It thus has the advantage of providing a smoother and more stable turf than conventional lawns of this type. The surface of the soil reinforced with this new mat is not encrusted, and a better aeration and moisture absorption guarantees fast and healthy growth of the grass seeds.

(2) Artificial ski slopes.--In order to practice the sport of skiing during non-winter months, various attempts have been made to cover a wide area of ground with mats of various kinds, e.g. rush mats, straw mats and coconut mats and more recently with materials composed of synthetic polymers. It is essential that mats of this type have outstanding sliding properties, resistance to abrasion, surface hardness, and other properties, such as being permanently resilient, rotproof and resistant to weathering. In addition, it should not be adversely affected by the very high temperatures generated during skiing.

Comb-like injection moldings have been used for this purpose which can be joined together to cover a large surface area. These moldings in the form of mats are intended to be rolled up for transporting and laying, but because of their looseness and extreme thickness of 3 to 6 cm., it is impossible to roll up in long lengths. Such molded mats are also fairly heavy and are therefore difficult to transport and lay on higher and steeper ski slopes. Furthermore, injection molding is quite expensive, and the necessity of carefully joining individual components also complicates the manufacturing process and increases the overall cost. Since no synthetic polymer is permanently resistant to weathering, especially with respect to sunlight, relatively frequent replacement is required even without hard abrasive use. For these reasons, mats prepared in this manner are too costly to be acceptable and widely used.

By using one of the mats according to the present invention, these problems are effectively solved. In particular, it is desirable to employ a coherent filamentary matting having the structure represented in FIG. 5 wherein the loops lying on the bottom surface of the matting are substantially parallel therewith to form a relatively firm and dense structure and the remaining loops extending toward the top side of the matting are gradually inclined at an angle of up to about 60 with reference to the top and bottom sides. In other words, the top layer of looped filaments should lie at an angle of not more than about 60 when the matting is placed on the ground.

This matting for artificial ski slopes is preferably made of polyamide filaments having an individual diameter of about 0.1 to 1 mm., preferably 0.2 to 0.8 mm., and can be produced in any desired thickness and weight by following the procedure described in connection with FIG. 2, i.e. with the use of an inclined guide plate adjusted to yield a maximum upper loop angle of 60. It has proven to be especially advantageous to use mats weighing from about 500 to 3500 and preferably about 1000 to 2500 grams per square meter, with a thickness ranging from approximately 1.5 to 5 cm. Other melt-spinnable polymers in addition to polyamides can be used where they possess sufficient strength and durability.

The upper surface of the matting while it is still deformable can be influenced by the application of light pressure, e.g. with the roller 17 shown in FIG. 2, not so as to form a completely smooth and flat surface but to preferentially bend the upstanding loops in one direction below the maximum angle of 60 required for this particular area of use.

These new mattings for ski slopes can be manufactured and laid in practically any length, and they are extremely easy to cut and/or piece together because the outer surfaces exhibit a suflicient number of projecting loops so that no joints are formed to interrupt thev uniformity of i the whole surface'area when lengths of matting are laid side by side. The matting is also extremely light in weight wax or similar lubricant. In order to prevent deterioration in bright sunlight to at least some extent, it is also desirable toincorporate anti-oxidants or other additives ineluding pigments and the like. Since deterioration cannot be completely prevented, the economical production and application of the matting of the invention for artificial ski slopes is a very significant and beneficial factor. Other areas of utility will be readily suggested by the matting product itself, and the invention offers a means of providing a relatively cheap and lightweight. reinforcing structure capableof'being manufactured with existing equipment supplemented by only minor changes or additions in the apparatus components and their combinations. Accordingly, the invention may be varied to achieve many different results within the spirit and scope of the appended claims.

The invention is hereby claimed as follows:

1. A process for the production of a matting of meltspun, substantially amorphous and continuous synthetic thermoplastic polymer filaments which comprises:

melt-spinning said filaments with a diameter of about 0.1 to 1.5 mm. vertically downwardly for deposit onto the bath surface of a liquid cooling medium from a plurality of spinning orifices arranged in at least three adjacent rows of approximately equidistantly spaced orifices, the upward buoyant force of said cooling medium being suflicient to cause said filaments to spread laterally in the form of sinuous to helical loops overlapping each other with reference to adjacent filaments in at least the same row;

completely solidifying the freshly spun filaments only after their entry into said cooling medium such that.

-near the surface of the cooling medium the filaments remain sufficiently tacky to adhere. to each other at their overlapping points of intersection; continuously withdrawing the melt-spun filaments through said liquid cooling medium in a path which diverges from the vertical direction of said meltspinning such that an outermost row of filaments forms a bottom layer of overlapping self-adhering looped filaments, each of the remaining rows of overlapping self-adhering looped filaments being positioned on top of and in adherent contact with the next-underlying row, the point at which the directionof withdrawal of filaments diverges from the vertical direction of rnelt spinning being located in a zone extending from about the surface of said bath down to a distance below said surface where said filaments are still sufiiciently plastic to be deformed; and removing the resulting mass of looped and layered filaments from said bath ofliquid cooling medium after the filaments have solidified sufliciently for adherent bonding into a continuous coherent matting.

the spinning orifices and the surface of the bath of bctween about 2 and 30 cm.

3. A process as claimed in claim 1 wherein the cooling liquid is water.

between all adjacent spinning orifices is about 3 to 15 mm.

6. A process as claimed in claim 1 wherein said bottom layer of an outermost row of filaments is brought into contact with a smooth-surfaced guide plate which extends at an angle to the surface of the bath of between about 10 and 80 to provide the diverging path of withdrawal of said filaments.

7. A process as claimed in claim 6 wherein the angle between said guide-plate and the surface of the bath is about 30 to 75.

8. A process as claimed in claim 6 wherein said guide plate intersects the surface of the bath approximately along the line projected on the surface of the bath by the. vertical 2. A process as claimed in claim 1 wherein said fila-' plane of the outermost row of freshly spun filaments such that said filaments are practically simultaneously deposited on the surface of the bath and brought into contact with said guide plate.

9. A- process as claimed in claim 8 wherein the line of intersection of said guide plate with said bath surface coincides exactlyv with the line projected on the surface of the bath by the vertical plane of the freshly spun outermost row of filaments.

10. A process as claimed in claim 8 wherein the outermost row of freshly spun filaments is brought into contact with said guide plate just beneath the surface of said bath.

11. A process as claimed in claim 8 wherein the outermost row of freshly spun filaments is brought into contact with said guide plate just above the surface of said bath, the linear distance between the points of contact and the surface of the bath along said plate being not more than the linear distance between said outermost row of filaments and the next adjacent row, and wherein additional cooling liquid is supplied over said plate to the filaments in contact therewith above ,the surface of the bath.

12. A process as claimed in claim 1 wherein a light pressure is exterted on the top row of overlappingselfadhering looped filaments during the formation of said matting at a point in said bath wherein said filamentsare still sufliciently plastic to be deformed but no longer tacky.

13. A process as claimed in claim 6 wherein a light pressure is exerted on the top row of overlapping selfadhering looped filaments during the formation of said matting at a point in said bath wherein said filaments are still sufiiciently plasticto be deformed but no longer tacky.

14. A process as claimed in claim 8 wherein a light pressure is exerted on the top row of overlapping selfadhering looped filaments during formation of the matting by a smooth-surfaced rotating roller at a point in said bath wherein said filaments are still sufficiently plastic to be deformed but no longer tacky.

15. A process as claimed in claim 6 wherein said guide plate has a'polished metallic surface for contact with said filaments. a Y

16. A process as claimed in claim 15 wherein said metallic surface is internally heated. I

17. A coherent filamentary matting which comprises a plurality of sinuously to helically looped, substantially amorphous and continuous filaments of a melt-spun synthetic thermoplastic polymer having an individual filament diameter of about 0.1 to 1.5 mm., said filaments being arranged in a number of superimposed contacting rows from bottom to top of said matting with overlapping intersection of the loops of adjacent filaments in at least the same row and with random self-adherent bonding of i 15 dividual filament diameter is between about 0.2 and 1 mm.

19. A matting as claimed in claim 17 wherein loops of approximately the same size are distributed uniformly through said matting to provide a uniform structure and uniform density. said loops projecting substantially laterally toward the top and bottom surfaces of the matting.

20. A matting as claimed in claim 17 wherein the loops on the bottom side of the matting are substantially parallel with the bottom surface to form a relatively firm dense structure and the remaining loops toward the top side of the matting extend at angles of up to 90 with reference to the top and bottom sides to form a structure of decreasing density from bottom to top.

21. A matting as claimed in claim 17 wherein the loops on both the top and bottom sides of the matting are substantially parallel with said sides to form a relatively compact and dense structure along either side, while the loops inside the matting extend at angles of up to 90 with reference to the top and bottom sides to form an intermediate structure of smaller density.

22. A coherent filamentary matting for artificial ski slopes as claimed in claim 20 wherein the loops extending toward the top side of the matting are inclined at an angle of up to about 60 with reference to the top and bottom sides, and wherein said matting has a thickness of about 1.5 to 5 cm. and a weight of approximately 500 to 3500 grams per square meter, the individual filaments having a diameter of about 0.1 to 1 mm.

,23. A matting for artificial ski slopes as claimed in claim 22 in which said filaments consist essentially of a fiber-forming polyamide.

24. A matting for artificial ski slopes as claimed in claim 22 wherein the individual filaments are coated with a wax.

25. A coherent filamentary matting for a transportable turf as claimed in claim 17 wherein the individual filaments have a diameter of about 0.1 to 0.8 mm. and the matting has a thickness of about 0.5 to 2.5 cm. and a weight of about to 500 grams per square meter.

26. A matting as claimed in claim 25 wherein the individual filaments have a diameter of about 0.2 to 0.5 mm.

27. A matting as claimed in claim 25 in which said filaments consists essentially of a fiber-forming polyamide.

References Cited UNITED STATES PATENTS 3,178,328 4/1965 Tittmann 156-181 X 3,026,272 3/1962 Rubens 260-25 2,473,528 6/1949 Hoover 154-101 2,923,093 2/1960 Allen 47-56 CARL D. QUARFORTH, Primary Examiner R. E. SCI-IAFER, Assistant Examiner U.S. Cl. X.R.

UNTTED STATES PATENT @FFTEE QERTTFTQATE F Patent No. 3, 91,004 Dated September 12, 1972 ln ventoz-(s) Helmut Werner, Hans Stapp v I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

molumn 1, line 8, insert Claims Priority Annli'cation Germany.....Nov. 26, 1968 P 18 10 921 Signed and sealed this 15th day of May 1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GDT'ISCHALK Attesting Officer Commissioner of Patents 

